HYBRIDS BETWEEN FUNDULUS AND MACKEREL 403 



Class C. In a sense this class is ahead of class B, but in another 

 ranks below it. Two individuals of a decided paleness and more 

 slender of body than those of class B have established a circula- 

 tion. The heart, however, is of small proportions and the red 

 blood corpuscles are few in number. The blood stream is quite 

 sluggish as compared with that in class A. The feature of most 

 significance in these embryos that marks them off sharply from 

 those of earlier classes is that they both exhibit paternal heredity, 

 in that green chromatophores are found scatteringly on the yolk, 

 but none on the body. The black and red chromatophores of 

 the maternal species greatly predominate. 



Class D. Eight individuals showing chiefly subnormal condi- 

 tions in the head region. The eyes are small or asymmetrical 

 in size or position; in one the eyes are very close together ap- 

 proximating a cyclopic condition. The hearts are typical string- 

 hearts pulsating vigorously. Both Fundulus and mackerel 

 types of black chromatophores are present in abundance, 

 but the maternal type predominates shghtly. Red Fundulus 

 chromatophores are more abundant than green mackerel chromat- 

 ophores, but the latter are present in abundance. 



Class E. A large group of forty-two individuals, all decidedly 

 subnormal in development, especially with regard to the most 

 anterior structures. The eyes are of various subnormal types: 

 microphthalmic, monophthalmic, cyclopic, or rudimentary. The 

 heart is at best a pulsating string-heart, btit in many cases no 

 pulsating tissues are noticeable. The posterior parts of the body 

 are in all fairly well grown. It is in this group that one finds the 

 most complex biparental combinations of chromatophores. 

 Both the Fundulus square and mackerel branched black chromat- 

 ophores are numerous, and both Fundulus red and mackerel 

 green chromatophores occur in abundance. Figures 2 and 3 

 represent two specimens that are quite . representative of this 

 class, drawn a few days after this first census was taken. One 

 specimen (fig. 2) has about the average condition for the class; 

 the reduced, somewhat vaguely defined head and eyes, the almost 

 equal balance between the maternal and paternal chromatophore 

 types being quite characteristic. The other specimen (fig. 3) a 



